Aircraft Retardation - Methods

[stuharri2002]

Dear all,

I would like to get a view of what is typically done with respect to slowing aircraft down on landing. Do you all use full thrust reverse? If thrust reverse is used, during what speed range is it used. Do spoilers stay activated until thrust reverse is taken out or longer? Also with regards to brakes, do you use AutoBrake LOW, MED or MAX, when do these come out and when does pedal braking occur?
I am trying to build up a picture of what happens, when, and during what speed range.

thanks for your help

stu

[Genghis the Engineer]

I've found a hedge particularly effective, but on the whole wouldn't recommend it.

G

[PPRuNeUser0172]

If you want an aircraft to be fully retarded, get BAe to make it;)

A drag chute is much more fun than any of the boring methods you refer to

DS

[ratarsedagain]

Stu,
On our A319/20's, the Ground Spoilers activate on t/d, and stay deployed 'til retracted by the pilot after vacating the r/w.
Usually use Low or Med auto brakes for landing (but sometimes manual more practical on a long r/w and vacating at the end for example). Med tends to be used on shorter or very wet r/w's or to reduce r/w occupancy. Max is for T/O only (in case of RTO).
Autobrakes can stay in to a full stop if necessary, but usually taken out when the pilot deems suitable, eg to get off at the required exit
Rev Idle as a min is always used, but sometimes Full to ease the heat build up on the brakes if the fans on them are u/s or not fitted. Bearing in mind that autobrakes give you a set rate of deceleration, so using full rev means the autobrakes applying to a lesser degree.
If full rev used, rev idle selected at 70kts, and forward idle at around 30kts.
Hope this helps,
Rat.

[TheOddOne]

Stu,

A slightly different perspective on your question.

From the airport operator's point of view, we design the turnoffs from the runway to be conveniently located to minimise the time that aircraft spend occupying the runway. We ask crews to plan the exit they are going to use and adjust braking accordingly. Of course this varies with conditions; headwind, runway state, landing mass (and hence speed). Very few aircraft need to use full power on reverse thrust. The major turnoff on 26L at LGW is designed to be taken at 60kt and the locally based crews will aim to be doing that as they start the turn from the centreline. If the reversers are still open then, it will be at idle.

The very worst thing crews can do is to come to a screaming halt and just miss an earlier turn, then have to apply power and dawdle up to the next turn. This can easily cause the next a/c to have to go around.

We had a 747-100 land some while ago and start the turnoff with a high power setting and the reversers still open. As the aircraft slowed, the hot gases being pushed forward started to be ingested and a thermal runaway occured. 2 engines caught light, pax down the chutes, broken ankles etc. Runway was blocked for a couple of hours. Thanks, guys.

I guess each type will come with appropriate warnings as to how reversers should be used. Of course, we've the luxury of a long runway. If LDA is limiting, then of course max retardation is required.

Another point is an environmental one. Because of our excess LDA we do ask crews to be economical with the use of reverse thrust during the night period, so as not to wake up the neighbours.

Cheers,
The OddOne

[dicksynormous]

The fastest way to make an aircraft retarded is to put a pilot in it:}

[Old Smokey]

stuharri2002,

The question that you've posed requires a general response as opposed to the specific one that you seek. It will depend on the aircraft type, and much more so upon the operational circumstances facing the pilot.

The nature of the brakes and the reverse thrust system will have a large influence upon the pilot's choice of the Brake / Reverser mix. Most pilots will use a bit of both, depending on their aircraft.

Carbon brakes are more effective than steel brakes, and wear LESS at high settings and speeds. Steel brakes wear more at high settings and speeds. It follows from this that a 'Carbon brake pilot' will be much more inclined to use heavier braking and less Reverse than a 'Steel brake pilot'. It saves money on maintainance, fuel, and noise. The 'Steel brake pilot', on the other hand would be more inclined to use less brake and more reverse, again in the interests of economics.

The type of reverser fitted will affect the pilot's emphasis on it's use. Even on the same aircraft type, customers can opt for 'Full" reverse of both core and fan flow, or just fan. The latter is the more common, and somewhat less effective than reversing all engine gases. Not so bad in the era of carbon brakes.

Having said all of that, common operational procedure with my company (B777-200/300) is to always use at least Idle Reverse. This negates the negative effects to deceleration of forward idle thrust without significantly changeing noise and fuel useage. Higher reverse settings all the way up to maximum are commonly used in line with the operational scenario, particularly on wet runways, short runways, or where it is highly desirable to make turnoff at a specific point. Reverse thrust is applied immediately upon touchdown, and reduced to idle by 60 Kt, unless an urgent situation develops whereupon full reverse may be used all of the way to a stop.

Regarding spoilers, they deploy automatically upon touch-down, and stay deployed until retracted during taxy by pilot selection. They do automatically stow if an aborted landing is executed after thrust levers go to 'Go Around'.

Auto-Brake is always used, on the B777 there are 5 numbered settings. There's no standard setting, 2 and 3 are the day to day settings depending on stopping capability required, with 4 for wet / down-sloping / down-wind runways. There's one more for the really bad day. Company philosophy is leaning more and more towards more brake and less reverse. Manual braking is effected at about 50 Kt Ground Speed, so that you can moderate the stopping distance remaining in line with distance to the turn-off point, common sense.

It all depends upon many many things.

[MeatHunter]

Genghis
Recently had to reskin the wing of a light a/c that had used a hedge to decelerate, only problem was that said hedge contained a rather large concrete fence post and left a sizable hole in the stbrd wing.
Moral of the story is to select hedges with big chunks of aforementioned material in them. They will stop quicker.
MH

[autoflight]

Reverse pitch on the piston engine powered Caribou is permitted after touchdown. 35 years ago in Vietnam it was not uncommon to select full reverse power together with full back stick, just before touchdown. I have personally observed many landing rolls less than 100 ft, but have also experienced [as PNF] one prop stuck in forward pitch. Don't try this at home!

[Loose rivets]

This thread has just brought back a horrible memory of my first command days on a Dak.

Taxiing at Amsterdam, Highway on the right - down below a steep bank; cars whizzing by. Strong X-wind. Left brake fading, more right engine. Going faster. Both of us standing on the left brake. Swinging right, more right engine...even better view of cars. More engine - more speed. Considered Mayday and taking off on taxiway. Considered throwing some of the bricks that I was sitting on, out and under the left wheel. Ug! Bag brakes.

[BOAC]

stu- It all depends upon many many things - to borrow Old Smokey's comment, one more factor to chuck in is the maintenance cost differential between engine useage in reverse and brake wear. Some SOPs will vary according to these factors.

Clever suits/beancounters in nice offices can spend glorious hours changing policies.:D

It all, however, does not stop the crew doing what they need to achieve what they need. As ratarsed said, if you are looking for quick t/rounds it is best to keep the brakes as cool as possible, hence more reverse.

[whitey05]

I have read in a lot of places that carbon brakes wear less at higher temperatures but no where seems to give an idea of what 'higher temperatures' are.
can anyone provide more information about this, what temperatures are best and what sort of level of wear is produced in comparison to steel brakes.

thanks

[md-100]

I love to use reverser thrust on the 737-200... It is music to my ears... although I try to use as less as necesary because of passanger confort. I always use MIN a/b (MED for contaminated rwys) and no when vacating at the end

[Dream Land]

From your original question I am assuming the Bus, OLD SMOKEY has once again said it far better than most of us could muster. Just two add my two cents worth, our aircraft have carbon brakes and we try to limit individual applications and brake riding whilst taxiing, our SOP's require us to do the following; be in REV idle by 70 and stowed by 60 due to avoid blade erosion and we stow spoilers after clearing the active.


Cheers, D.L.:cool:

[OverRun]

whitey05

Try this for more on carbon brakes
http://www.pprune.org/forums/showthread.php?s=&threadid=109138

[Shiny side down]

A variety of factors involved.

With the Auto brake providing a rate of deceleration, more reverse means less brake activity to achieve the same deceleration rate.
That means that brakes can be kept cooler, so there are no limitations on turnaround while waiting for brake cooling.
Especially useful if the turnaround is tight as seems often the case these days.
However, for noise abatement, some airports are now implementing the requirement of no reverse thrust to be used (unless necessary for safety reasons). This is often all day, not just night ops.
Therefore, autobrakes are providing the deceleration rate, Idle reverse being used as standard. That way any positive thrust is negated. I presume there is a small benefit in drag/ reverse flow, and they are deployed should everything go pear shaped.

on th B737NG autobrake 1,2,3,max,RTO
1 is lowest programmed deceleration rate.
3 is the highest programmed rate.
Max is the brakes driven to max available braking, protected by the antiskid.
RTO is obviously rejected takeoff.

The QRH has braking distances depending on brake selection.

As a guide, Brakes 1 or 2 seem most common for the majority of destinations we go to.
1 especially if the most appropriate turnoff is a long way down the runway. 2 if the most appriate turnoff is nearer.
Auto Brakes disabled by 60kt is common. Or if there is an overriding reason to control the brakes manually.

[Dan Winterland]

Manufacturers generally recommend use of autobrake and idle reverse. This is because the amount of applications of carbon brakes is more significant in reducing wear than the temperature they reach. Autobrake gives you a selected decceleration rate (on the A320, low gives you 1.7metres per second per second for example). Autobrake comes on soon after landing, the reversers take a while and by the time the reversers have taken effect, braking is already under way. The result is that the brakes release a bit to maintain the decceleration rate but the landing run is exactly the same. When the reversers are stowed at typically 70 knots. However, you have changed the brake setting and increased wear.

The trick is to make your turnoff at about 30 knots (70 in Ryanair's case!) achieving the above.

The A380 has an 'exit by' function. You tell the FMGS which exit you wish to use and the autobrake gives you one steady application to make that exit.

[Tarnished]

No one has touched on my favourite which is aerodynamic braking, not a big hit in the airline/truckie world but in the sharp pointy world works well F-15, Jag, Typhoon the latter two when you add a brake chute make the difference between 1000 deg brakes and 100 deg brakes.

T

[Swedish Steve]

Back in the early 80's I used to work at Bahrain and handled LTU Tristars routing Mahe- Bahrain-Dusseldorf. I always remember that they kept the nose up for ages as they went down the runway with the engines at reverse idle. When they arrived on the gate the brakes were cold. We refuelled them during a 30 min transit as the crew stayed on board. Never see anyone doing it nowadays.

[738Capt]

Stoping an aircraft on a runway can be done with autobrakes only. The settings for autobrakes slow the aircraft down at different rates, measured in kts per meter. ie 20kts in 60 meters.

737 does not require reverse thrust nor speedbrakes to stop the aircraft, but the brake ware is much greater.

I fly domestic flights around Australia both Virgin Blue and Qantas use full reverse thrust (some aitlines use reverse idle) upon touchdown as well as spoilers. Reverse thrust is canceled at 60kts and taxi speed is about 20kts.

[Old Smokey]

737 does not require reverse thrust nor speedbrakes to stop the aircraft
No civil aircraft requires reverse thrust to stop the aircraft. Aircraft certified under FAR 25 (or it's equivalent) do not take credit for reverse thrust in the Landing Performance certification. Reverse thrust is a bonus, as is any AFM data providing you with landing distances using reverse thrust.

Regards,

Old Smokey

[skiesfull]

I certainly would not try exiting LGW or anywhere else via a R.E.T. (rapid exit turn) at the maximum 60 knots in a 747 or other wide-bodied type. Whilest the use of reverse is not factored into certification, speedbrakes or more correctly, ground-spoilers, are. From the Boeing Flight Crew Training Manual for the 747-400 "unless speedbrakes are raised after touchdown, braking effectiveness may be reduced initially as much as 60%".
As the old adage goes "bang it in, stand on them and slam them into reverse!" then leave the runway quietly and wait for the complaints from the cabin crew!!

[Shiny side down]

I knew I was doing it right:O